using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.UI;
public class ShowMessage
{
/// <summary>
/// 自定義彈出窗口內容
/// </summary>
/// <param name="msg"></param>
public static void AjaxShow(string msg)
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "alert('" + msg + "');", true);
}

/// <summary>
/// 自定義彈出窗口內容并直接轉向一個新的頁面
/// </summary>
/// <param name="msg"></param>
/// <param name="url"></param>
public static void AjaxShow(string msg, string url)
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "alert('" + msg + "');javascript:location='" + url + "';", true);
}

/// <summary>
/// 自定義彈出窗口內容并選擇是直接轉向，還是提示轉向一個新的頁面
/// </summary>
/// <param name="msg"></param>
/// <param name="isreturn"></param>
/// <param name="url"></param>
public static void AjaxShow(string msg, bool isreturn, string url)
{
if (!isreturn)
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "alert('" + msg + "');javascript:location='" + url + "';", true);
}
else
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "if(confirm('" + msg + "')){javascript:location='" + url + "';}", true);
}
}

/// <summary>
/// 自定義彈出窗口內容，自定義是否關閉當前頁面
/// </summary>
/// <param name="msg"></param>
/// <param name="close"></param>
public static void AjaxShow(string msg, bool close)
{
if (close)
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "alert('" + msg + "');javascript:window.close();", true);
}
else
{
ScriptManager.RegisterStartupScript((System.Web.UI.Page)HttpContext.Current.CurrentHandler, typeof(System.Web.UI.Page), "ShowMessage", "alert('" + msg + "');", true);
}
}
}

如果出現"ScriptManager"是未知元素在 web.config文件中的system.web節點中加上

 <pages>

      <controls>

        <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

      </controls>

    </pages>

說明文檔：http://www.cnblogs.com/kenwong/articles/2773705.html